1. Field of the Invention
The present invention relates generally to a map display terminal and a map display method. More particularly, the invention relates to a map display method for displaying a map corresponding to a current position on the basis of a current position information.
2. Description of the Related Art
In the recent years, an apparatus displaying a current position utilizing a Global Positioning System (GPS) technology has been widely spreading primarily for vehicular navigation system. In such apparatus, a map data to be displayed is stored in a storage medium, such as CD-ROM or the like so as to display a corresponding map on the basis of a current position information obtained by GPS.
On the other hand, in addition to application for the vehicular navigation system, a handy type map display terminal has been put into practical use. Since these apparatus are required to be portable, the apparatus are compact to be impossible to store all of map data, amount of which is huge. Therefore, these apparatus are designed to download the necessary map data by means of communication means.
As advantage of a system, in which the map data are arranged in a map server on a network and is downloaded as required, the latest map data can be constantly provided, and the user may able to obtain the latest map data constantly. It is also possible to distribute real-time information, such as traffic information or the like by embedding in the map data.
In case of the handy type map display terminal set forth above, in which the map data is downloaded, portability of such type of the map display terminal is essential to make a display area narrow to cause difficulty of displaying information of a destination and facilities, such as railway station, intersection and so forth, to be landmarks, in one picture frame. Therefore, when map display is performed taking the destination (current position) at the center of display, difficulty is encountered in detecting the relationship with the peripheral condition.
On the other hand, in case of the handy type map display terminal set forth above, until completion of downloading of the map data for initially displaying the map after completion of downloading, the user may not be able to check the progress of downloading.
Therefore, the present invention has been worked out for solving the problems set forth above. It is an object of the present invention to provide a map display apparatus and a map display method which facilitates detection of relationship between the destination (current position) and the peripheral condition even when a detailed map is to be displayed on the narrow display area.
Another object of the present invention is to provide a map display apparatus and a map display method which permits to check progress of downloading of detailed map information.
According to one aspect of the invention, a map display terminal for displaying a current position on a map by deriving the current position on the basis of a position information from a Global Positioning System, comprising:
first means for displaying a wide area map having smaller reduced scale than a detailed map and centered at the current position upon displaying the detailed map centered at the current position.
In the preferred construction, the map display terminal further comprises second means for displaying the initially displayed wide area map with expansion in step-by-step manner until the detailed map is displayed. The second means may include means for downloading detailed map information from a server storing the detailed map information.
The map display terminal may be a portable communication terminal. In such case, a communication between the portable communication terminal and the server is performed through a portable telephone network. In the alternative, the communication between the portable communication terminal and the server is performed through a packet network.
The second means may expands display of the wide area map in step-by-step manner depending upon progress of downloading of the detailed map information. The second means may include means for calculating an expansion ratio at each display stage on the basis of a ratio of reduced scales of the wide area map and the detailed map, number of display stages, progress of downloading.
According to the second aspect of the present invention, a map display method for displaying a map of a current position by deriving the current position on the basis of a position information from a satellite, comprises:
first step of displaying a wide area map having smaller reduced scale than a detailed map and centered at the current position upon displaying the detailed map centered at the current position.
The method preferably further comprises second step of displaying the initially displayed wide area map with expansion in step-by-step manner until the detailed map is displayed. The second step may includes step of downloading detailed map information from a server storing the detailed map information. In such case, a communication between the portable communication terminal and the server is performed through a portable telephone network. In the alternative, the communication between the portable communication terminal and the server is performed through a packet network. The second step may expand display of the wide area map in step-by-step manner depending upon progress of downloading of the detailed map information. The second step may include step for calculating an expansion ratio at each display stage on the basis of a ratio of reduced scales of the wide area map and the detailed map, number of display stages, progress of downloading.
According to the third aspect of the present invention, a storage medium storing a map display control program for displaying a map of a current position by deriving the current position on the basis of a position information from a satellite, the control program comprising:
first step of displaying a wide area map having smaller reduced scale than a detailed map and centered at the current position upon displaying the detailed map centered at the current position.
The storage medium may further comprise second step of displaying the initially displayed wide area map with expansion in step-by-step manner until the detailed map is displayed.
Namely, the map display method according to the present invention displays the wide area map centered at a particular position, such as destination, current position or so forth, with expansion in step-by-step manner depending upon progress of downloading upon downloading the detailed map information from the map server.
More particularly, in the map display method according to the present invention, when the detailed map (wherein, the detailed map has a larger arithmetic value of its scale ratio than a wide area map. For example, the arithmetic value of a scale ratio of {fraction (1/100)} for the detailed map is larger than the arithmetic value of a scale ratio of {fraction (1/10,000)} for a wide area map.) centered at the particular position detected by the GPS in response to the demand of the user, at first, demand for the detailed map data is performed for the map server, and at the same time, the wide area map (wherein, the wide area map has a smaller arithmetic value of its scale ratio than a detailed map. For example, the arithmetic value of a scale ratio of {fraction (1/10,000)} for the wide area map is smaller than the arithmetic value of a scale ratio of {fraction (1/100)} for a detailed map.) preliminarily stored in the terminal is displayed.
Subsequently, in the map display method according to the present invention, the wide area map is displayed with expansion in step-by-step manner depending upon the progress of downloading of the detailed map data. After completion of downloading, the detailed map is displayed.
By this, even when the detailed map is displayed on the narrow display area, a relationship between the particular position, e.g. destination or current position and the peripheral condition, can be easily seen. Also, progress of downloading of the detailed map can also be seen easily.